(1) Field of the Invention
The present invention relates to an image information processing apparatus such as a copier, printer, facsimile machine, scanner and the like as well as relating to a sheet feeder usable in an image information processing apparatus and having a function of feeding sheets, one by one, from a stack of sheets.
(2) Description of the Related Art
Concerning image information processing apparatuses including: a copier which scans the image of an original and produces a printed output of the scanned image information; a printer which produces a printed output of transferred image information; a facsimile machine which transmits the image information obtained by scanning the image of an original; and a scanner which scans the image of an original to obtain its image information and the like, wasted interior space is attempted to be reduced as much as possible to make the image information processor compact. However, when miniaturizing, simply reducing the space is not effective enough, it is necessary to develop the miniaturization whilst securing necessary space, without any deterioration of the functions and operativities as much as possible.
For example, in order to enable maintenance, checks, adjustment, repair etc. of an image processing apparatus, Japanese Utility Model Laid-Open Application Sho 58 No. 126,460 discloses an image processing apparatus in which its functional units can be detachably attached from two adjoining sides thereof. In this prior art, when the detachable photosensitive member unit is attached or detached from the top of the image processing apparatus, the functional unit, located below the photosensitive member inside the image processing apparatus and having functional parts, are shifted to the side of the image processing apparatus while the developing unit is pulled out of the top, so as to create an open space around the photosensitive member for its attachment and detachment. Thus, the photosensitive member is attached or detached.
Concerning this technology, in order to improve the easiness of the attachment and detachment by reducing the number of working steps upon attachment and detachment, it is possible to configure an arrangement in which the photosensitive member can be attached and detached from the top of the image processing apparatus without shifting the functional unit, including the functional part located below the photosensitive member, to the side of the image processing apparatus. Illustratively, the functional parts, including the photosensitive member, located above the photosensitive member are integrated into a single functional unit so that the unit can be attached or detached from the top of the image processing apparatus. In such an image processing apparatus, it is necessary to develop miniaturization without compromising the attachment and detachment performance.
However, in the case where the image processing apparatus having detachable functional blocks, disclosed in Japanese Utility Model Laid-Open Application Sho 58 No. 126,460 is miniaturized, in order to effect the function in the functional unit, the parts inevitably residing at their predetermined positions are kept as they are while parts other than the above-mentioned parts are configured to be moved. Further, in order to avoid interference of one functional unit with an adjacent one during attachment and detachment thereof, each functional unit is configured so as not to have any projection which would be an obstacle to the attaching or detaching movement of an adjacent functional unit and hence the functional unit is preferably configured so that the width of the space required for attachment and detachment may be substantially uniform. Therefore, the overall shape of functional units tends to be a rectangular prism. However, if the functional units are limited to this shape, they produce wasted space. In this way, it was not possible to reduce the volume of the space occupied by the functional units, and hence it was not promoted to miniaturize of the image processing apparatus. This problem becomes marked for the functional units having functions relating to the sheets, such as an exposure scanner unit, sheet feeding unit, image forming unit, fixing unit and the like.
For miniaturization of the image information processing apparatus, the following two points are of importance:
(1) To miniaturize individual parts; and PA0 (2) To eliminate the wasted space within the image information processing apparatus as much as possible. However, the first point `miniaturization of individual parts` can be attained only to a limited extent, limited by the fact that each part should present the specified functionality expected by the design requirements.
For the purpose of explanation, a feed roller in a sheet feeding device having the function of separating and feeding sheets, one by one, from a stack of sheets will be a typical example. The sheet feeding performance of a feed roller varies widely depending upon the size of the sheets (length, width and thickness), the characteristics of sheets (friction coefficient with respect to the feed roller and the stiffness) or the environment under which sheets are handled by the feeder. Therefore, in order to expect a stable sheet feeding performance for handling a variety of sheet types under various environment conditions, the feed roller needs certain minimum dimensions. For example, to prevent skew during feeding, the feed roller needs to abut the sheet with a predetermined nipping length or greater, which means that the feed roller needs to be longer than a predetermined length. To separate sheets, one by one, the feed roller needs to abut the sheet with a predetermined nipping width or greater, which means that the diameter and the rubber thickness of the feed roller need to be greater than predetermined values.
Concerning the sheet stopper means of a sheet feeder for preventing the stack of sheets from reaching the feed roller, this device needs to move and retract from the sheet blocking position when a sheet needs to be delivered. Therefore, the movable distance of the stopper is determined by the height of the stack of sheets to be allowed. As for some examples of the functional parts disposed in the image forming units, such as the photosensitive member, the developing roller in the developing unit, the cleaning blade, the charger, the transfer device, etc., the sizes of these elements are determined by the maximum size of sheets to be handled since image forming needs to be done for the sheets of the acceptable maximum size.
In this way, not only the functional parts directly acting on the sheets, such as the feed roller, photosensitive member, charger, transfer device etc., but also the functional parts indirectly acting on the sheets, such as the developing roller, cleaning blade etc., will be determined as to their dimensions by the size of the sheets to be handled. Further, similar to the sheet stopper means, there are functional parts having a predetermined movable range. But the movable range is also determined depending on the sheets. Accordingly, these functional parts relating to the sheets, because they relate to sheets, may be modified as to their dimensions and their positional relationship relative to the sheets, to some permissible extent depending upon their relationship with the sheets, but still cannot be said to have a large flexibility in their design.
On the other hand, parts other than the functional parts relating to the sheets, such as, the drive transmitting parts for transmitting driving force to the functional parts relating to the sheets, support parts and casings for accommodating functional parts relating to the sheets, drive sources, parts for electrical connections and the like, are rather flexible in design with regard to miniaturization and their layout, compared to the functional parts relating to the sheets.
Next, the second point, `elimination of the wasted space within the image information processing apparatus as much as possible` will be discussed.
In the interior of an image information processing apparatus, there are many functional units which each can be attached and pulled out integrally and still have both the functional parts relating to the sheets and the other parts. Each functional unit having these functional parts relating to the sheets tends to have unused spaces, but these spaces are scattered. Therefore, the volume of unused spaces unnecessarily has made the image information processing apparatus bulky.
Further, due to the possibility of malfunction from the increase of the number of working steps and complexity of working procedures at attachment and detachment of a functional unit, the simplest handling during attachment and detachment of the functional unit is the main matter of interest during design. As a result of this, if a functional unit has a projected portion in the mid part thereof with respect to the direction of the sheet width, around other adjacent components in the image information processing apparatus, the functional unit is disposed apart from other adjacent components so that the projected portion will not interfere when it is attached and detached. Accordingly, wasted space arises between adjacent functional units; this has also made the image information processing apparatus bulky.
The above described problem will now be described taking a specific example of a sheet feeder comprising a pickup feeding means, a separation feeding means and a sheet stopper means, all being the functional parts directly acting on sheets.
A sheet feeder for separating and feeding sheets, one by one, from a stack of sheets placed on a sheet stacking means, in the downstream direction with respect to its conveyance, is disclosed in Japanese Patent Publication Hei 6 No. 71,947. In this sheet feeder, the pickup feeding means is disposed on the upstream side of the separation feeding means for separating sheets, one by one, with respect to the sheet conveying direction, and the pickup feeding means moves from a position away from the top of the sheet stack on the sheet stacking means, to the abutting position on the sheet stack so as to deliver a sheet toward the sheet separation feeding means. The pickup feeding means of this sheet feeder is configured to move up and down as it rotates about a rotary axle.
In general, since such a sheet feeder handles sheets of regular sizes, it is not possible to reduce the dimensions with respect to the planer directions of the sheets, to smaller than the maximum size of the sheets to be handled, but a miniaturization (development of a thinner configuration) can be expected with respect to the direction of the sheet thickness.
Now, the development of thinning a sheet feeder having an up-and-down moving type pickup feeding means, disclosed in Japanese Patent Publication Hei 6 No. 71,947 will be considered. When considering the facts that the dimensions of the separation feeding means and pickup feeding means are considerably smaller than the maximum acceptable sheet size and that the pickup feeding means moves up and down, the sheet feeder tends to have wasted space on both sides of the pickup feeding means with respect to the direction perpendicular to the sheet conveying direction. Since other devices and components also tend to occupy a considerably large space in the central portion with respect to the direction perpendicular to the sheet feeding direction within the image processor, it is difficult to lay out devices and components other than the sheet feeder, in the spaces on both sides of the pickup feeding means because of the consideration of attaching and detaching performance of the devices and components disposed inside the image processing apparatus.
When the up-and-down driver and/or drive source of the pickup feeding means were laid out on both sides of the pickup feeding means, the up and down driver and drive source, in general, were arranged in both sides of the pickup feeding means with respect to the direction perpendicular to the sheet feeding direction, rather near the center in proximity to the pickup feeding means. Accordingly, this up-and-down driver and drive source were the obstacles to further miniaturization.
Further, the pickup feeding means and sheet stopper means disclosed in Japanese Patent Publication Hei 6 No. 71,947, are configured so as to move between the active position where they act on the sheets and the inactive position where they are away from the sheets. The pickup feeding means, separation feeding means and sheet stopper means do not extend across the full width of the acceptable maximum sheet size, but are formed with certain dimensions, with respect to the direction of the sheet width, which are shorter than the maximum sheet width. On the other hand, with regards to the direction of the sheet thickness, since the pickup feeding means and sheet stopper means move up and down, the spaces occupied by these components, when considering the space of their movable ranges, are bulky in their mid parts compared to other parts. If another functional unit needs to be disposed adjoining this sheet feeder, the functional unit must be arranged apart therefrom so that the space for movement of this functional unit will not interfere with this bulged portion of the sheet feeder. This produces wasted space.
In the sheet feeder disclosed in Japanese Patent Publication Hei 6 No. 71,947, the mechanism for shifting the positions of the pickup feeding means (pickup roller) and the sheet stopper means (shutter 12), are arranged close to the pickup feeding means and the sheet stopper means with respect to the direction of the sheet width. Further, the mechanism for transmitting a driving force for moving the stopper means, is constructed so that the driving force from the drive source is transmitted by combination of a rotary transmitting element and a rotary drive transmitting element (in Japanese Patent Publication Hei 6 No. 71,947, the drive transmitting element of the pickup feeding means is a first cam 39 while the drive transmitting element of the sheet stopper means is a second cam 72). Because of these arrangements, the shifting mechanism is comparable to or greater in size than the pickup feeding means and sheet stopper means.
Next, another case will be explained in which a rotary drive transmitting element and a solenoid as the drive source are arranged adjacent to a pickup feeding means with respect to the direction of the sheet width. Now, the factors hindering the development of a thinner configuration of the sheet feeder with respect to the direction of the sheet thickness will be described with reference to FIGS. 1 and 2.
FIG. 1 is a perspective view showing a sheet feeder in a conventional copier, and FIGS. 2A and 2B are sectional views of the operating states of this sheet feeder. FIG. 2A shows the case where the pickup feeding device is in its non-pickup state, and FIG. 2B shows the case where the pickup feeding device is in its pickup state.
In this manual feeder, a pickup feeding means 152 picks up sheets P from a stack of sheets placed on a sheet stacking means 151 to a separation feeding means 153, where the sheets are separated and fed, one by one, towards the downstream side with respect to the sheet conveying direction.
Pickup feeding means 152 is rotatably supported about a rotary shaft, i.e., drive input shaft 701 by means of support members including the rotary shaft, support arms 700 for supporting the rotary shaft and a coupling plate 705 for coupling the arms. Pickup feeding means 152 is configured so that it can be moved by a solenoid 702, a return spring 703, a rotary shift lever 704 and an urging spring 706, between the active position where the pickup feeding means abuts sheets P stacked on the sheet stacker and the inactive position where it is kept away from sheets P. This configuration is further detailed below.
Rotary shift lever 704 can be engaged with part of the supporting means (coupling plate 705 in this case) of pickup feeding means 152. When solenoid 702 is activated, rotary shift lever 704 rotates counterclockwise in FIG. 2, opposing the elastic force of return spring 703 so as to disengage the supporting means of pickup feeding means 152. Upon this disengagement, the rotatably supported pickup feeding means 152 comes down due to gravity acting on the support members and pickup feeding means 152 itself and due to elastic force of urging spring 706 so as to press sheets P (at the active position) enabling the feed of the sheets.
When solenoid 702 is deactivated, rotary shift lever 704 is turned clockwise in FIG. 2 by the elastic force of return spring 703, and separates pickup feeding means 152 away from the sheets and returns it to the inactive position, opposing the gravity acting on pickup feeding means 152 itself and the support members and the elastic force of urging spring 706.
Suppose that solenoid 702 is designed so as to be activated to output a driving force to rotate the rotatable portion rotating integrally with pickup feeding means 152 upperwards and hence separate pickup feeding means 152 from the sheet. In this case, an elastic means such as a spring etc., urging pickup feeding means 152 toward the sheets is needed, so the driving force needs to oppose the urging force from the elastic means urging the pickup feeding means 152 toward the sheets and also oppose gravity acting on the portion integrally rotating with pickup feeding means 152. Under consideration of this fact and also considering the duty ratio of solenoid 702 or the activation of solenoid 702 when the manual feeder is not used, the solenoid 702 inevitably needs to be made large or high powered. Therefore, to avoid this situation, solenoid 702 is adapted to become active when the manual feeder is used, so that the portion rotating integrally with pickup feeding means 152 is designed to move upwards by means of spring 703 coupled to shift lever 704. In this case, solenoid 702 only needs to have a driving force for rotating the shift lever, opposing only spring 703, so a low powered solenoid 702 is adequate for this operation.
Depending upon the length of active duration of solenoid 702 and/or the size of solenoid 702, the following limitations need to be imposed for making solenoid 702 compact.
That is, when solenoid 702 is directly coupled with rotary shift lever 704 as stated above, the solenoid needs be active when pickup feeding means 152 moves to the active position (since the time during which the solenoid is in the inactive position is overwhelmingly longer than that in the active position). For this purpose, the plunger which is at the mid point of the height of solenoid 702 must rotate rotary shift lever 704 in the counterclockwise direction so that the plunger is disposed below the rotary shaft of rotary shift lever 704.
As seen from FIG. 2, if the location of the solenoid 702 is set downward, the open space for passing the sheet therethrough becomes narrow. So it is impossible to dispose solenoid 702 and rotary shift lever 704 below the space for stacking sheets. Yet, pickup feeding means 152 needs to be configured so as to move down to sheet stacker 151.
Even if a solenoid 702 of a compact type is used, the size is considerably larger when compared to the size of pickup feeding means 152.
Because of these conditions and requirements, rotary shift lever 704 and solenoid 702 will project upwards above the level of pickup feeding means 152 when it is positioned at its highest position, i.e., the inactive position. Accordingly, the actual height of the sheet feeder, with respect to the direction of the sheet thickness becomes greater by the dimension of the aforementioned projection.
In FIG. 1, the driving force for turning separation feeding means 153 and pickup feeding means 152 when feeding sheets is input from the machine body side by means of a clutch etc.
Next, the sheet stopper means as a functional part which is disposed in the sheet feeder and moves between the active position and inactive position will be described.
When sheets are stacked on the sheet stacking means, the sheets are pushed in to the position of the sheet separation feeding means. The sheet stopper means of the sheet feeder is to prevent erroneous feed such as multifeed and the like when sheet feeding is started. Therefore, the stopper means needs to be positioned on the upstream side, with respect to the sheet conveying direction, of the separation feeding means. On the other hand, the stopper means needs to be laid out on the downstream side, with respect to the sheet conveying direction, of the pickup feeding means, in order to enable the pickup feeding means to feed the topmost sheet from the sheet stacking means when sheet feed is started. Accordingly, the stopper means is arranged between the pickup feeding means and separation feeding means. In the case of a feeder of this mechanism, the pickup feeding means is supported by the support assembly so as to come into and out of contact with the sheets. Therefore, as disclosed in Japanese Patent Publication Hei 6 No. 71,947, the known stopper means is configured to be coupled with the support assembly pivotally provided on the separation feeding means side so as to go from above the sheet stacking means down to between the pickup feeding means and separation feeding means.
The use of this mechanism, however, makes the sheet feeder thicker with respect to the direction of the sheet thickness because the support assembly of the stopper means rotates and moves over the separation feeding means. Further, since the sheet stopper means is configured to rotate and move up and down, when a stack of sheets is placed on the sheet stacking means, the stopper means is liable to move upwards when pressed by the sheets, which would cause mal-feeding of sheets.
Up to now, negative factors in miniaturizing the sheet feeder which moves between the active and inactive positions were discussed. All the other functional units of the image information processing apparatus have hindering factors against their miniaturization.
For solving the above problems concerned with miniaturization of the image information processing apparatus, it is necessary to improve the design flexibility of each functional unit having functional parts relating to the sheets, especially that of the parts other than functional parts relating to the sheets in that unit. More specifically, it is necessary to prevent the parts other than functional parts relating to the sheets from becoming projected into the center with respect to the direction of the sheet width, and hence prevent functional units from becoming bulky. That is, it is necessary to design the layout so that parts other than functional parts relating to the sheets will not produce wasteful space between adjoining functional units.